Performing femtosecond laser-assisted keratoplasty for keratoconus

Take-home: A retrospective study evaluating outcomes in patients with keratoconus found that when compared to femtosecond laser-enabled keratoplasty (FLEK), femtosecond laser deep anterior lamellar keratoplasty (FsDALK) had similar overall visual and refractive outcomes with a statistically significant lower overall graft rejection rate.

In eyes with keratoconus, femtosecond laser deep anterior lamellar keratoplasty (FsDALK) has been found to have the same visual outcomes as femtosecond laser-enabled keratoplasty (FLEK) and a lower rate of graft rejection, according to findings of a retrospective study from investigators at the University of California, Irvine.

The researchers compared the two procedures in eyes requiring keratoplasty in patients with keratoconus, who were either contact lens intolerant or possessed a visually significant central corneal scar. The study was made up of 36 eyes of 34 patients (mean age 36 years) who underwent FsDALK and 127 eyes of 107 patients (mean age 44 years) who underwent FLEK.

Follow-up visits occurred at post-operative months 1, 3, 6, 9, 12, 18, 24, 30 and 36. Outcomes assessed included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent (SE), manifest and topographic cylinder, and comparison of graft rejection rates. The proportion of eyes available for follow-up in both groups fell to <50% after the 18-month post-operative visit and only 9 FLEK eyes and 4 FsDALK eyes were evaluated at the 36-month mark.

“This is one of the few studies looking at visual and refractive outcomes in FsDALK and FLEK in keratoconus patients,” said Soroosh Behshad, MD, MPH. “It had good patient follow-up with adequate samples sizes for the first 18 months postop that slowly declined thereafter up to the 3-year mark. We had a higher success rate with DALK when the femtosecond laser is utilized, and this may allow for more widespread adoption of this technique.”

Dr. Behshad was involved in the study as a clinical instructor at the Gavin Herbert Eye Institute, University of California Irvine under the mentorship of Marjan Farid, MD. He is now assistant professor of ophthalmology at Emory University, Atlanta.

For both FLEK and FsDALK, the zig-zag incision was utilized for laser trephination of both the host and donor tissue. For the FsDALK procedure, the zig-zag incision was combined with Anwar’s “big bubble” technique.

Despite the potential for an optical interface in the DALK patients, the study found no statistically significant difference in visual outcomes when FsDALK was compared to the full thickness technique. CDVA was similar in the two groups throughout follow-up, both in terms of rapid visual recovery and no statistically significant difference between FsDALK and FLEK.

SE on average, was found to be slightly more myopic in the FsDALK group, with no statistically significant difference between the two groups. The FsDALK group on average had a slightly lower amount of measured topographic astigmatism. However, no statistically significant difference was found for either topographic or manifest astigmatism between the two groups.

Throughout the follow-up, FLEK eyes had lower average keratometry values than the FsDALK eyes.

The rate of graft rejection was significantly higher in the FLEK group than in the FsDALK eyes (14.2% versus 5.6%; p < 0.05). Of those instances of graft rejection that could not be reversed medically, the incidence of graft rejection requiring regrafting was also lower in the FsDALK group than in the FLEK group (2.8% versus 4.7%%; p > 0.05).

“The overall graft rejection rate in the FLEK group appears to be slightly on the higher end of what has been reported in the literature for penetrating keratoplasty. The outcome may be explained by the lower average age of our study’s patients as well as the use of a larger diameter (9 mm) graft,” Dr. Behshad said. “Regardless of that issue, the present comparison demonstrates a lower overall graft rejection rate in a younger sample size in the FsDALK group, which may be explained by prevention of an endothelial immune reaction when the host endothelium is preserved. Overall, it seems that younger keratoconus patients would benefit from FsDALK with good visual outcomes and low rejection rates.”

Soroosh Behshad, MD, MPH  

E: soroosh.behshad@emory.edu

This article is based on a presentation given by Dr. Behshad at the 2016 annual meeting of the American Society of Cataract and Refractive Surgery Symposium. Dr. Behshad has no relevant financial interests to disclose.